1. Field of the Invention
The present invention relates to a washer pump for sucking washing liquid stored in a washer tank and injecting it from a nozzle. The present invention also relates to a filter used for the washer pump.
2. Related Art
This type washer pump is disclosed in Japanese Utility Model Publication No. H02-60659U shown in FIGS. 13 and 14. As shown in FIG. 13, this washer pump 1 is attached via the cylindrical communicating member 6, the outer circumference of which is engaged with the liquid discharge port 5b formed on the side wall 5a of the washer tank 5. The pump case 2 of this washer pump 1 includes: a motor chamber 2a accommodating the armature 3 rotating when electricity is supplied to it; and a pump chamber 2b accommodating the impeller 4 rotating being coupled to the armature shaft 3a of the armature 3. The cylindrical liquid suction port 2c communicating with the pump chamber 2b is inserted into the inner circumference of the communicating member 6. As shown in FIG. 14, the filter 7 for filtering washing liquid W is arranged in the communicating member 6.
When a predetermined intensity of electric power is supplied from the connector 2e for supplying electric power to the washer pump 1 via a switch not shown in the drawing, the armature 3 is rotated and the impeller 4 is rotated in the pump chamber 2b. When the impeller 4 is rotated, washing liquid W stored in the washer tank 5 is sucked from the liquid suction port 2c into the pump chamber 2b. At the same time, washing liquid W is discharged from the liquid discharge port 2d communicated with the pump chamber 2b. Washing liquid W, which has been discharged from the liquid discharge port 2d, is supplied to the nozzle 9 flowing in the liquid supply pipe 8 and injected from the nozzle 9 to a washing face not shown in the drawing.
While washing liquid W is being sucked from the liquid discharge port 5b of the washer tank 5 into the liquid suction port 2c of the washer pump 1 via the communicating member 6, foreign objects such as dust are removed and filtered by the mesh-like filtering portion 7a of the filter 7 provided in the communicating member 6. Therefore, no foreign objects are sucked into the pump chamber 2b of the washer pump 1. Due to the foregoing, the occurrence of damage of the impeller in the pump chamber 2b caused by the mixed foreign objects can be prevented. Also, the occurrence of blinding of the nozzle 9 can be prevented.
However, in the case of the aforementioned conventional washer pump 1, a centrifugal type washer pump is adopted, the suction pressure of which is so low that the sucking operation cannot be performed. Therefore, when the washer pump 1 is operated, it is impossible for the centrifugal type washer pump to let air out of the pump chamber 2b so as to reduce the pressure in the pump chamber 2b to be negative. Therefore, the impeller 4 is idly rotated, and it is impossible to discharge washing liquid W from the liquid discharge port 2d of the pump chamber 2b. Especially in the case where the mesh-like filtering portion 7a is arranged in the communicating member 6 or a check valve is arranged in the liquid supply pipe 8 for communicating the pump chamber 2b with the nozzle 9 is arranged, when washing liquid W is poured into the washer tank 5, a water film formed on the filter 7 by the action of surface tension can not be torn away even when the washer pump 1 is operated, and the impeller 4 is idly rotated and washing liquid W can not be discharged from the liquid discharge port 2d of the pump chamber 2b. In the conventional washer pump, this phenomenon remarkably appears.